The inherent space, weight, and materials standards relating to aircraft service dictate specialized designs for what would otherwise become a perfunctory operation. In the case of an aircraft instrument rack, maximum utilization of the available space for instruments dictates a convoluted, difficult area in which to fit ventilation ducts. Ideally, the ducts will be sturdy, yet flexible enough to fit any path, no matter how tortous Federal Aviation Administration requirements must be met, and the duct will ideally be non-metallic in order to avoid electromagnetic interference with avionics equipment.
Many ducts and tubes have been used in the past to form a flow path for many types of fluids. Each application has its related requirements. For example, U.S. Pat. No. 4,691,741, entitled "Shroud for Aircraft Duct" to Affa et al., discloses a shroud especially resistive if Skydral hydraulic fluid, which forms an air insulating gap. U.S. Pat. No. 4,699,567, entitled "Fan Duct Casing" to Stewart, discloses a containment ring for a gas turbine engine fan duct.
U.S. Pat. No. 4,615,359, entitled "Shroud for Aircraft Duct" to Affa et al., discloses a wrapping for the titanium shrouds of aircraft ducts to guard against corrosion. U.S. Pat. No. 4,121,606, entitled "Inflatable Air Inlet Duct" to Holland et al., discloses a movable air inlet duct, while U.S. Pat. No. 4,185,373, entitled "Method of Manufacturing an Inflatable Air Inlet Duct" to Holland et al., discloses the method of manufacture of same.
U.S. Pat. No. 4,582,297, entitled "Tape and Method for Measuring and/or Pulling Cable" to Conti, discloses a tape made of warp and weft threads made of polyamide fibers, for use in pulling a duct along an overhead support. U.S. Pat. No. 4,693,941, entitled "Reinforced Poly(Ethylene Terepthalate) Compositions" to Ostapchenko, discloses polyethylene terepthalate compositions usable as a protective covering.
U.S. Pat. No. 4,714,094, entitled "Gas-Oil Pressure Acumulator" to Tovagliaro, discloses the wrapping of a metallic vessel with composite carbon fibers, especially Kevlar. U.S. Pat. No. 4,717,764, entitled "Two Stage Melt Polymerization Process for Making Polymers Containing Aromatic Amide Groups" to Ward, discloses a two stage process of reacting and then heating until the desired viscosity is reached. U.S. Pat. No. 4,718,818, entitled "Containment Structure" to Premont, discloses a structure wrapped with fiber, especially Kevlar, under tension to withstand the force of particles impinging upon it.
U.S. Pat. No. 4,755,082, entitled "Removable Bottom Founded Structure" to Beskow et al., discloses a Kevlar woven tube for use in a drilling platform. U.S. Pat. No. 4,734,007, entitled "Fan Casing and Fan Blade Loading/Unloading" to Perry, discloses woven fibrous material for a fan casing utilizing Kevlar fibers.
Each of the above applications was appropriate for its associated environment, but a duct meeting stringent aircraft requirements which also has a high degree ease of use is still lacking in the aircraft industry.